Apparatus for heating gases



April 14, 1931.

w. A. DARRAH APPAATUS FOR HEATING GASES Original Filed May l2 1926 Patented Apr. 14, 1931 PATENT OFFICE WILLIAM A DARRAH, OF CHICAOO, ILLINOIS APPARATUS FOB HEATING GASES Application led Hay 12, 1926, Serial No. 108,618. Renewed November 8, 1928.

This invention relates to apparatus for heating gases or vapors and provides improved devices for obtaining high degrees of eliiciency with a minimum amount of fuel and with a minimum investment in equipment.

Some of the objects of this invention are to secure a large heat transfer with a relatively small heater, to permit clean and smokeless combustion of fuel, and to allow heating of gases or vapors with a minimum resistance as the gases or vapors travel through the equipment. Another object of this invention is to reduce the cost of equipment by making the heat transferring surfaces as edective as possible. Other objects will be apparent from the description, claims, and drawings.

This equipment may be used either as a socalled direct heater in which the products of 29 combustion are mixed with the circulating gases to be heated or it may be used as an indirect heater in which the products of combustion are kept separate from and not mixed with the gases or vapors to be heated.

The apparatus disclosed in this invention, may be used in connection with patent #1,524,340, Patent #1,57 1,57 5, or in any other desired application.

Referring to the drawing, Figure I, shows a plan view in section, of an air heater constructed in accordance with this invention. Figure II, shows an end elevation in section, while Figure III, shows a side elevation also in section.

In the drawing (1) indicates a housing arranged to inclose the combustion chamber and other portions o the heater. A combustion chamber (2) is located within housing (1) and supplied with fuel through a .burner (3) 'l located adjacent to combustion block (4),

and arranged to deliver air and uel in proper ratio to combustion zone (5). Products of combustion travel in the manner shown by the dotted arrows.

Combustion zone (5) is connected by opening (6) to zone (7), and zone (7) in turn is connected with zone (8) by opening (9). Walls (10) and (10A) are located between zones (5) and (6) and zones (7) and (8) respectively.

After leaving zone (8) products of combustion which have traveled through zones (5) and (7 enter distributing flue (11) and pass upward through ducts or pipes (12) to stack base (13) and then to stack (14). 55

Duets or pipes 12) may be supported by partitlon (15) at t eir top end and mounted in partition (16) at their lower end. Partitions (15) and (16) serve to separate the flue gases and products of combustion from the gases or vapors being heated, and flues or pipes (12) are normally inserted in partitions (15) and (16) in lsuch a manner that the joint is substantially tight as far as the travel of appreciable quantities of gas or vapor is concerned.

Flues or pipes (12) may to advantage be y made of different materials in that the lower portion designated as (17) may be of heat resisting materials such as special alloy, while 0 the upper portion (18) may be of steel or less expensive metal than the lower ortion (17 Portions (17) and (18) may be connected by any form of union or coupling as indicated at (19). 75

The dotted opening indicated by (20) serves as a removable connection between the combustion chamber and the passageway in which the gases to be heated circulate. When this device is operating as a direct heater tile (20) may be moved into position shown 1n dotted lines at (21) and the products of combustion will then be free to enter the space occupied by the circulating vapors or ases which are being heated. 85 i On the other hand, when the device is serv- V lng as a direct heater tile (20) is in a position shown in the solid lines making it impossible for any appreciable quantity of products of combustion to mix with the gases or vapors being heated.

The gases or vapors which are to be heated may enter through duct or opening (22) and travel in a direction shown by the solid arrows leaving through duct or opening It will be understood that the direction of flow of vapors or gases being heated may be reversed although in ordinary use the direction shown has proven very satisfactory since it provides a counter-current low causing the products of combustion to travel in a general direction which is contrary to the :flow of gases or vapors being heated.

I have found it advantageous to construct combustion chamber (2) from materials having a high heat conductivity such as silicon carbide, heat resisting alloys, etc., choosing of course materials which will stand a high degree of heat. It will be understood that this device is not limited to one combustion chamber as as many combustion chambers may be used as conditions require, depending upon the amount of air to be heated, etc.

I refer to keep combustion zone (5%) open insidh, and empty and free from central obstructlons of any kind, in order to provide ample volume for combustion without causing combustion to take place in contact with solid walls. This point is essential in. burning fuel oil or powdered coal, but in the case of gas is not essential and I, therefore, do not wish to restrict this design in this manner, exclusively.

I have found further that it is of decided advantage to place central restrictions or baffles in zones (7 and (8). In these zones the combustion is normally completed or substantially completed, and the temperature of the gases which result from combustion is much lower having lost a considerable amount of the initial heat by radiation and convection to the walls and top of zone (5) of combustion chamber Since the products of combustion have lost a port-ion of their heat they occupy a smaller volume. I have found therefore that by adding central ballie or fiue (24) in zone (7 and increasing this width as shown at (25) near the end of zone (7 and the beginning of zone (8) that great improvements can be obtained in heat transfer. I have found that this condition can be carried, to advantage, still further by increasing the size of the central baffle as shown at (26) in zone (8). It will be evident that by the device of the central baffles which may be preferably perforated and irregular on their surface, the products of combustion are forced to travel in close contact to the outer walls of the combustion chamber and thus give up their heat much more readily than would otherwise be the case.

It is not feasible under practical conditions to reduce the width of the lower zones, such as zones (7) and (8) because of obvious structural reasons. It is also usually undesirable to reduce the height of zones (7) and4 (8) as this reduces the amount of surface available for transferring the heat from the flue gases to the gases or vapors being heated.

The use, therefore, of the central baille accomplishes the desirable result in a practical and effective manner without reducing the area of the combustion chamber Walls or the width of the lower combustion zones.

I have found it desirable to place the inisible to place combustion zone (5) at the bot' tom of combustion chamber 2) allowing the products of combustion to travel upward as shown in the case .of Patent #1,57 1,57 5.

In either case, the central obstructing piers i or balles placed in the cooler zones are equally desirable and satisfactory.

It will be understood that one of the objects in securing the maximum heat transfer through a given square foot of combustion chamber surface, is to reduce the cost of the equipment for the reason that the combustion chamber should preferably be made of materials which are both ood heat conductors and very refractory. ll commercial materials having these properties to a marked degree are relatively costly and it is, therefore, essential to use as little of them as possible, or what brings the same result, to make each unit as effective as possible. This result also produces a smaller and more compact heater which has less weight and occupies less space.

From the standpoint of combustion the central retarding baffle placed in zones (7), (9), etc., also prove effective in increasing the efficiency of combustion, and the completeness with which the fuel is burned. This results in practically eliminating smoke, soot, or dirt, and makes it possible to freely mix the products of combustion with the recirculated air or gases which may be used for drying or other purposes.

Obviousl the presence of soot and dirt in the recircu ating gases would be very objectionable.

While the internal baffle serves in many ways to improve combustion, it is probably that one manner in which it achieves this result depends on the retarding of the flow of gases, thus providing sufficient time for combustion to be completed. It is Well known that the act of combustion requires a definite time and it is further recognized that if suficient time is not permitted Within the combustion chamberfor combustion to be completed this defect is not corrected after the gases leave the combustion chamber. The inner baffle, therefore, serves to retard to a controlled degree the exit rof gases from the combustion chamber, thus serving to improve combustion conditions.

The inner baiie also acts in another manner 1n that 1t serves as a reservoir or storage iop from hot gases to ,of heat compensating for inequalities in the rate of feeding fuel or air.

As a general principle, it may be stated that the inner baflle should be designed in such a manner as to maintain ap roximatcly equal velocities in the products o colnbustion passing through the combustion chamber. This, of course, means that the free cross section of the combustion chamber passages decreases rogressively from the inlet, or point at which the hot gases are delivered, to the outlet or point at which the leave. It is not essential that the inner ba e be regular or conform with mathematical exactness to the temperature of the gases. In fact it is advantageous to construct the inner baffle in such a manner that it presents a roughened and irregular surface to the flow of gases, thus causing eddies which serve to retard and break up a stream line iow.

To explain, non-technically, one effect of the inner baiie, it may be stated that it serves to prevent the formation of a core of gases which would otherwise pass through the center of the combustion chamber zones without coming into effective contact with the combustion chamber walls. Such a core would not deliver its heat to any large extent to the combustion chamber walls as experience has proven that heat is transferred principally solid walls by convection.

Without wishing to be conlined to any specific velocity for the products of combustion, I would state that from 1000 to 2000 feet per minut-e in general gives satisfactory results.

In this specification and claims, I have used the term heat resisting material to indicate a substance which may be either carborundum, refractories, or alloys, such as chrome iron, or chrome nickel alloys, etc., in distinction to iron or steel which in commercial par lance are not considered heat resisting materials.

It will be understood that I do not wish to confine this invention to the specific form illustrated and described, as many modifications will be apparent to those skilled in the art and should be construed to fall within the scope of this invention. I specifically do not wish to be limited to any special material or materials as the description and drawing are intended only to illustrate the general features of this invention.

Having now fully described my invention what I claim as new and wish to secure by Letters Patent in United States is as follows:

1. A device for heating gases or vapors consisting of a housing, a combustion chamber within said housing, passages around said combustion chamber for said gases to be heated, a flue connecting said combustion chamber to a vent, and an inner baffle of varying section located within said combustion chamber, said section of said baille being greatest adjacent the discharge end of said combustion chamber and least adjacent aid entering end of said combustion cham- 2. In a device for heating gases and vapors a combustion chamber of substantially uniform exterior section, but having an interior section varying from a maximum at the hot zone to a minimum at the cooler zone.

3. A device for heating gases consisting of a housing, a combustion chamber within said housing, gas passages around said combustion cham er, a heat supplying device located adjacent to the upper portion of said combustion chamber, an outlet to a stack located adjacent the lower portion of said combustion chamber, and a ta ered baffle positioned within said combustion chamber.

4. In a device for heating gases a combustion chamber of heat resisting material arranged with a fuel supply device located near its upper portion, an outlet near its lower portion leading to a flue, and means for maintaining approximately uniform velocity in the flue gases passing through said combustion chamber.

5. A device for heating gases, consisting of a housing, a heat resisting combustion chamber having walls of relatively good heat conducting material located within said housing, a fuel supply device located adjacent the upper portion of said combustion chamber, downwardly leading passageways within said combustion chamber near its lower portion connecting with a flue, and upwardly leading heat radiating members arranged between said combustion chamber and a stack.

6. In a heat resisting combustion chamber a baflie of varying cross section said cross section being a minimum adjacent the hot portion of said combustion chamber and a. maximumadjacent the discharge end of said combustion chamber.

7. In a heat resisting combustion chamber a symmetrically arranged internal baie of varying section, said baffle being smallest at the hottest end and largest at the coolest end.

8. In a device for heating gases, a heat resisting combustion chamber consisting of a plurality of connected, substantially horizontal passageways, a fuel feeding device located near the upper end, and a flue connection near the lower end, and a longitudinal bafe of varying cross section, located within said combustion chamber.

9. A device for heating gases consisting of a housing surrounding a combustion chamber composed of a plurality of connected substantially horizontal chambers, a fuel feeding device near the upper portion of said combustion chamber, a flue connecting to the lower portion, a baille of varying section within said combustion chamber, heat radiating members connected to said chamber, and passage for gases to be heated i around said radiating members and said combustion chamber.

10. A device for heating gas consisting of a housing, a heat conducting member of refractory material within said housing and connected to a fuel supply device at the upper portion and at the lower portion to a series of metal heat radiating members, and a passage for gases to be heated by said heat conducting member. j t

11. In a gas heater, a combustion chamber of heat resisting material, a passage for gas being heated adjacent to said combustion chamber walls and heated thereby, a fuel supply device arranged near the upper portion of said combustion chamber, a baille wall within said combustion chamber, and. an exit opening for products of combustion, near the lower portion of said combustion chamber.

12. In a gas heater, a combustion chamber, a passage for gas beingheated adjacent to said combustion chamberwalls and heated thereby, a fuel supply device feeding said combustion chamber, and connected near the upper portion thereof, and an outlet for the gases from said combustion chamber at a point below said fuel supply device.

13. In a gas heater, a heat resisting combustion chamber, a fuel supply device connected neaa` its upper portion, an outlet port near its lower portion, said chamber being so arranged that products of combustion travel downward from said fuel supply device toward the lower portion of said combustion chamber, and a passageway for gas being heated in contact with the walls of said combustion chamber.

14. In a gas heater, a heat resisting combustion chamber, a fuel supply device connected near its upper portion, an outlet port near its lower portion, said chamber being so arranged that products of combustion travel downward from said fuel supply device toward the lower portion of said combustion chamber, a passage for as being heated in contact with said com ustion chamber, and an insulated housing surrounding said combustion chamber, and said gas passage.

15. In a gas heater, a housing, a gas inlet, a gas outlet, a combustion chamber within said housing, a fuel supply device feeding said combustion chamber, a passage for gas to be heated, separate means for reducing the temperature -of products of combustion from said fuel supply device by transmission directly from said combustion chamber to said passage, and an outlet port for said products of combustion below said fuel supply device arranged to cause the products of combustion from said fuel supply device to travel downward.

16. A device for heating gases, consisting of a housing, a heat resisting combustion chamber, a passage for gas t0 be heated in contact withvsaid combustion chamber, a fuel supply device located adjacent the upper portion of said combustion chamber, downwardly leading passageways within said combustion chamber near its lower portion, connecting with a flue.

17. In a gas heater, a laterally extending combustion chamber of heat resisting material, a fuel supply device at one end thereof, a free primary combustion space therein adjacent to said fuel supply device, a constricted portion adjacent the other end of said chamber and beyond said combustion space retarding the exit of products of combustion from said combustion chamber, and a gas passage for the gas to be heated in contact with said combustion chamber.

18. A device for heating gases consisting of a housing, a combustion chamber within said housing, gas passages around a portion of said combustion chamber, a heat supplying device located adjacent to the upper portion of said combustion chamber, and an outlet to an exhaust port located adjacent the lower portion of said combustion chamber.

19. A device for heating gases or vapors in which combustion products without substantial loss in heat and immediately adjacent their source are brought into heat exchange relation with the gases or vapors to be heated, comprising a housing and within the housing walls defining a combust-ion chamber and passages for the gases to be heated which passages are in general horizontally arranged beside the said chamber and beyond the wallsv thereof, a passage for conducting heated products of combustion horizontally and bustion chamber to an outlet near the bottom of said housing, and means for effecting heat interchange between the products of com'- bustion and the gases to be heated during the horizontal travel of the gases. and the said horizontal and downward travel of the combustion products within the housing.

20. A device for heating gases or vapors in which combustion products without substantial loss in heat and immediately adjacent their source are brought into heat exchange relation with the gases or vapors to be heated, comprising a housing, walls of refractory material defining a com-bustion chamber within said housing, heat interchange elements for the gases to be heated which elements are also within the housing beside said combustion chamber spaced therefrom and protected by a wall thereof from direct radiation of the heat of combustion within said chamber, a passage for conducting heated products of combustion into heat exchange contact with said elements, and means for circulating the gases to be heated through the housing and within the same into Contact with the heated surfaces downwardly from the comof the heat exchange elements and out of contact with the heating medium therefor.

21. A device for heating gases or vapors in which combustion products Without substan- 5 tial loss in heat and immediately adjacent their source are brought into heat exchan e relation with the gases or vapors to e heated, comprising a housing, Walls of refractory material dening a combustion chamber Within said housing, heat interchange elements for the gases to be heated which elements are also Within the housing beside said combustion chamber spaced therefrom and located substantially within the vertical dimension thereof, a passage for conducting heated products of combustion into heat exchange contact with said elements, and means for circulating the gases to be heated through the housing and Within the same into contact with the heated surfaces of the heat exchange elements and out of Contact With the heating medium therefor.

WILLIAM A. DARRAH. 

